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<title>Screen shots of the Querypoint Firebug Extension prototype</title></head>
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<img src="1-bp22.jpg"/>
<p>A screen shot of the Firebug debugger The Script
  panel is selected; it gives access to
  all loaded source files and allows breakpoints to be set on lines. In this
  figure, the execution is paused at line 22 by a regular
  breakpoint. The Watch panel at the right shows the program state at
  the paused
  point. Developer can query <i>lastChange</i> on a <code>myObject.myProperty</code> by right-clicking on the value of <code>myProperty</code>.
  </p>

<img src="3-lastChange.jpg"/>
<p>
The result of <i>lastChange</i> query for
  <code>myObject.myProperty</code>. The left panel, QP, shows the source
  code at the point of <i>lastChange</i>; The right panel,
  TraceData, shows the collected data at the
  point.
</p>
<img src="4-lastChange2.jpg"/>
<p>
The result of <i>lastChange</i> query for
  <code>myCondition.value</code>. To evaluate an expression (e.g., oldValue) at this point, developer can
  enter the expression in the watch box and after re-execution the result is available.
  The opened list on the top of the left panel shows the visited execution points. Clicking on each point in
  the list shows the corresponding code and
  data.
</p>
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